ch 2 single-gene inheritance

Question 1

chromatin

Answer 1

the substance of chromosomes
- now known to include DNA and chromosomal proteins

Question 2

histone

Answer 2

a type of basic protein that forms the unit around which DNA is coiled in the nucleosomes of eukaryotic chromosomes
- H1 histone - make sure the nucleosomes get lined up correctly

Question 3

nucleosome

Answer 3

the basic unit of eukaryotic chromosome structure; a ball of eight histone molecules that is wrapped by two coils of DNA
- associate with and coil around H1 histone

Question 4

telomere

Answer 4

chromosome end

Question 5

centromere

Answer 5

area of constriction

Question 6

nucleolar organizer

Answer 6

tandem repeats of rRNA genes

Question 7

heterochromatin

Answer 7

dense chromatin
- will appear darker with stain, more constricted

Question 8

euchromatin

Answer 8

less dense chromatin

Question 9

true-breeding

Answer 9

genotype is homozygous

Question 10

dominant phenotype

Answer 10

the parental phenotype that is expressed in a heterozygote

Question 11

dominant allele

Answer 11

an allele that expresses its phenotypic effect even when heterozygous with a recessive allele
- is A is dominant over a, then A/A and A/a have the same phenotype

Question 12

recessive phenotype

Answer 12

the parental phenotype that is not expressed in the heterozygote

Question 13

recessive allele

Answer 13

an allele whose phenotypic effect is not expressed in a heterozygote

Question 14

first filial generation (f1)

Answer 14

the first generation resulting from a controlled cross between two known parents

Question 15

second filial generation (F2)

Answer 15

the second generation resulting from a controlled cross between two known parents, generated by selfing/intercrossing the F1 generation

Question 16

product rule

Answer 16

the probability of two independent events occurring simultaneously is the product of their individual probabilities

Question 17

sum rule

Answer 17

the probability that one or the other of two mutually exclusive events will occur is the sum of the individual probabilities

Question 18

Mendel’s law of equal segregation

Answer 18

two members of a gene pair segregate equally into the gametes, so that half the gametes carry one allele and the other half of gametes carry the other allele
-each parent contributes 1 copy of each factor to offspring with equal frequency
- gametes are haploid, fuse to form diploid offspring

Question 19

test cross

Answer 19

a cross of an individual organism of unknown genotype or a heterozygote with a tester

Question 20

tester

Answer 20

an individual organism homozygous for one or more recessive alleles

Question 21

Mendel’s overall conclusions (5)

Answer 21

1. difference btw yellow and green traits is that they carry a discrete and different hereditary determinant (mendel’s particulate factors)
2. factors exist in pairs
3. in each pair, one of the factors is dominant to the other (recessive and dominant alleles)
4. parents pass one copy of each factor onto offspring; diploids produce haploid gametes, that have one cope of each gene, or one member of each homologous pair
5. factors from parents unite independently of the type of factor; gametes fuse randomly

Question 22

chromatid

Answer 22

one of the two side by side replicas produced by chromosome replication

Question 23

sister chromatids

Answer 23

the juxtaposed pair of chromatids arising from the replication of a chromosome

Question 24

homologous chromosomes

Answer 24

chromosomes that pair with each other during meiosis and (usually) have the same genetic loci (may have different alleles)

Question 25

dyad

Answer 25

a pair of sister chromatids joined at the centromere

Question 26

tetrad

Answer 26

four homologous chromatids in a bundle in the first meiotic prophase and metaphase

Question 27

chiasma

Answer 27

a cross-shaped structure commonly observed btw non sister chromatids in meiosis - the site of crossing over

Question 28

s-phase

Answer 28

DNA molecules replicate to form identical chromatids - making a copy of the existing DNA

Question 29

molecular marker

Answer 29

a site of DNA heterozygosity (difference), not necessarily associated with phenotypic variation, used as a tag for a particular chromosomal locus

Question 30

hemizygous gene

Answer 30

a gene that is present in only one copy in a diploid organism

Question 31

reciprocal crosses

Answer 31

a pair of crosses of the type genotype A (female) x genotype B (male) and B (female) x A (male)

Question 32

prophase

Answer 32

- chromatids coil and condense to become visible - mitotic spindle forms outside of nucleus, consists of microtubules - nuclear envelope breaks down and nucleoli disappear - kinetochores form on each face of the centromere

Question 33

kinetochore

Answer 33

multiprotein complex that binds to centromere - site of attachment for microtubules

Question 34

metaphase

Answer 34

- chromosomes align along the metaphase plate

Question 35

anaphase

Answer 35

- centromeres and sister chromatids separate from chromosomes

Question 36

telophase

Answer 36

- migration of chromosomes to the poles is complete - nuclear envelope reforms

Question 37

cytokinesis

Answer 37

cellular division takes place to form the 2 new daughter cells (genetically identical)

Question 38

mitosis generates

Answer 38

cells identical to mother cell

Question 39

interphase

Answer 39

G1, S, G2

Question 40

M phase

Answer 40

1. prophase 2. metaphase 3. anaphase 4. telophase

Question 41

meiosis generates

Answer 41

haploid cells from diploid

Question 42

MI

Answer 42

align and separate homologous pairs - reduced division

Question 43

MII

Answer 43

separate sister chromatids - equational division

Question 44

prophase 1 (5 phases)

Answer 44

leptotene, zygotene, pachytene, diplotene, diakinesis

Question 45

leptotene

Answer 45

chromosomes condense - become visible

Question 46

zygotene

Answer 46

pairing of homologues, crossing over - synaptonemal complex begins to form

Question 47

pachytene

Answer 47

synaptonemal complex complete (compressed)

Question 48

diplotene

Answer 48

slight separation of synaptonemal complex to form chiasmata

Question 49

diakinesis

Answer 49

further contraction of synaptonemal complex (compressed again)

Question 50

synaptonemal complex is made of

Answer 50

DNA and protein

Question 51

function of the synaptonemal complex

Answer 51

facilitates crossing over

Question 52

metaphase 1

Answer 52

- homologs move to the equatorial plane - centromeres attach to the spindle - line up as tetrads

Question 53

anaphase 1

Answer 53

- one homolog moves to each pole - sister chromatids DO NOT separate - separate homologous pairs (still dyads)

Question 54

telophase 1

Answer 54

- migration complete - nuclear membrane MAY reform - cytokinesis MAY occur

Question 55

prophase 2

Answer 55

condensed chromosomes

Question 56

metaphase 2

Answer 56

dyads aligned along equatorial plane

Question 57

anaphase 2

Answer 57

separation of centromeres and sister chromatids - results in two chromosomes

Question 58

telophase 2

Answer 58

nuclei reform cytokinesis to produce 4 haploid daughter cells

Question 59

sex-linked single-gene inheritance patterns

Answer 59

genes that show different phenotypic ratios

Question 60

autosomal dominant pedigree

Answer 60

1. trait appears in every generation 2. affected parents have affected children 3. no correlation between sex and a particular phenotype

Question 61

x-linked recessive pedigree

Answer 61

1. phenotype is more common in males than females 2. affected fathers have no affected children - however, all daughters are carriers 3. trait passed from grandfather to grandson

Question 62

x-linked dominant pedigree

Answer 62

1. fathers pass traits to all daughters - however, no sons are affected 2, mothers pass trait to half sons and daughters

Question 63

y-linkage

Answer 63

no conclusive cases 1. phenotype passed from father to all sons - not to daughters